What do you think about these two places? American coffee vs. Canadian coffee perhaps?
Personally, I like Starbucks better. I've never been a big fan of coffee. For me, they're just bitter black liquids that can condition your body to be more alert. Nope……black coffee are never pleasant to have.
What I do like from Starbucks are their delicious Frappuccino~ 
They're sooooo good. The best ones I love are the Banana & Cream as well as the Strawberry & Cream. Some of the people I know say the Starbucks latte and Frappuccino are too heavy…which may be true. However, after comparing the nutrition menu for both restaurants, I think if you drink the same amount of beverage (be careful with cup sizes, Starbucks follow the American standards, their small is bigger than a Tim Hortons large!), then the calorie/fat contents are actually relatively similar. In a few cases, the Starbucks' beverages actually appear to be healthier.
The good side about Tim Hortons are their freshly baked goodies. Their donuts and bagels are baked daily in the back of each local store. Starbucks….as far as I know, do not bake their muffins and cookies in their local stores, so the food you get are not as fresh.
Final ratings? Beverage - STARBUCKS! Baked goodies - Tim Hortons.
P.S. You do have to keep in mind though….Tim Hortons is primarily a coffee place, if all you wanted were baked cookies and bread…why not visit a real bakery?!